JPS6319687B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine equipped with a supercharger, and more particularly to a supercharged engine suitable for using a mixed fuel of alcohol and gasoline.

Recently, engines equipped with a supercharger that supercharges intake air into the combustion chamber have been developed in automobiles and the like. For example, a turbine installed in the exhaust passage drives a blower installed in the intake passage to supercharge the intake air. Engines equipped with turbochargers have been developed. This type of engine increases engine output by using exhaust gas to drive a blower via a turbine, and by sending air to the engine body in a supercharging manner using the blower driving force according to the amount of exhaust gas. . In this case, the output increases as the boost pressure increases, but if the boost pressure increases too much, problems such as impairing the durability of the engine will occur, so the boost pressure should not be increased beyond a certain point. It is necessary to control the maximum boost pressure. For this reason, conventionally, for example, a bypass passage is provided in the exhaust passage to bypass the turbine, and the bypass passage is equipped with a control device that bypasses the exhaust gas when the boost pressure exceeds a set value. When this point is reached, the control device operates to release part of the exhaust gas to the bypass passage, and a means for suppressing the driving force of the supercharger prevents the supercharging pressure from rising above a predetermined value.

Incidentally, in recent years, the use of a mixed fuel of alcohol and gasoline has been proposed to compensate for the shortage of gasoline resources, but when using this mixed fuel in the supercharged engine, the following problems arise. was left behind. That is, alcohol has a lower calorific value than gasoline, and as the alcohol concentration in the mixed gas increases, the output tends to decrease, so a means to increase the output is required to compensate for this. On the other hand, since the mixing ratio of alcohol and gasoline may vary depending on the filling station or the like or due to the phenomenon of separation of gasoline and alcohol, it is necessary for the engine to work effectively even when the mixing ratio changes in this way. However, in the conventional structure as described above, if the maximum boost pressure is limited by the control device so as to be suitable when the alcohol concentration is relatively low or when using gasoline alone, it is difficult to control the mixture with a high alcohol concentration. If fuel is used, the maximum output due to the maximum boost pressure will be insufficient, and if the maximum boost pressure is always set high to be suitable for mixed fuel with a high alcohol concentration, it will not be possible to use mixed fuel or gasoline with a low alcohol concentration. When a single fuel is used, there are problems such as deterioration of engine durability as described above.

In view of these circumstances, the present invention uses a boost pressure control device in an engine equipped with a supercharger to adjust the maximum boost pressure to prevent excessive load from being applied to the engine. When using mixed fuel with gasoline, when the alcohol concentration increases, the control characteristics of the boost pressure control device are corrected accordingly to increase the maximum boost pressure and compensate for the decrease in output. It is an object of the present invention to provide a supercharged engine that can effectively use mixed fuels and gasoline of various concentrations.

That is, the present invention includes a supercharger that supercharges intake air into a combustion chamber, and suppresses an increase in supercharging pressure when the supercharging pressure of the intake air supercharged by the supercharger is equal to or higher than a set value. In a supercharged engine equipped with a boost pressure control device, a fuel supply device that supplies a mixed fuel made by mixing alcohol and gasoline, an alcohol concentration sensor that detects alcohol concentration,
a correction device configured to correct the control characteristics of the boost pressure control device based on the output of the sensor, and to increase the set boost pressure of the boost pressure control device when the alcohol concentration is above a predetermined value. It is characterized by having the following configuration.

Embodiments of the present invention will be described below with reference to the drawings.

1 is an engine body, 2 is an intake passage that takes air into the engine body 1 from the outside, and 3 is an exhaust passage that discharges exhaust gas from the engine body 1. Further, 4 is a supercharger, and in the embodiment shown in the figure, a turbo supercharger is used, which includes a turbine 5 installed in the exhaust passage 3, a blower 6 installed in the intake passage 2, and The turbine 5 is rotated by the exhaust gas, and the blower 6 is rotated in conjunction with the turbine 5, thereby forcing air to be forced into the engine body. I am trying to send it to 1.

Reference numeral 8 denotes a carburetor as a fuel supply device, which vaporizes a mixed fuel of alcohol and gasoline sent from a fuel tank (not shown) and sends it into the intake passage 2. Normally, the carburetor 8 is positioned downstream of the blower 6 in the intake passage 2 to avoid contamination of the blower 6 with fuel. 9 is a throttle valve that is linked to an accelerator pedal or the like.

This supercharged engine also includes a supercharging pressure control device 1 that suppresses an increase in supercharging pressure when the supercharging pressure of the intake air supercharged by the supercharger 4 exceeds a set value.
1, and this boost pressure control device 11 is equipped with a relief valve 1, for example, in a bypass passage 10 formed in the exhaust passage 3 so as to bypass the turbine 5.
2 is provided, and the opening and closing pressure of the valve 12 is controlled by a spring 13 that applies a constant pressing force in the valve closing direction and a pressure chamber 14 that opposes the spring 13. The pressure chamber 14 communicates with the intake passage 2 via a conduction passage 15 that is sufficiently thinner than the intake passage 2. With such a structure, the boost pressure control device 11 opens the valve 12 when the pressure in the intake passage 2 reaches a set value, and the pressure in the pressure chamber 14 increases accordingly, thereby releasing a portion of the exhaust gas. The intake air is bypassed to the bypass passage 10, thereby controlling the rotational speed of the turbine 5 and the blower 6, and working to suppress the intake air supercharging amount.

The boost pressure control device 11 includes an alcohol concentration sensor 16 that detects the alcohol concentration in the mixed fuel of alcohol and gasoline, and corrects the control characteristics of the boost pressure control device 11 based on the output of the sensor 16. A correction device 17 is provided.
The sensor 16 itself for detecting the alcohol concentration is known in various ways, and for example, one that detects the alcohol concentration by measuring the dielectric constant of the mixed fuel, or any other suitable detection means may be employed. This sensor 16 may be provided in the float chamber of the carburetor, the fuel tank, or the like.
Further, the correction device 17 includes, for example, a control circuit 18 that operates upon receiving a signal from the sensor 16 when the alcohol concentration exceeds a predetermined value, and an actuator 19 that is operated by the control circuit 18. The actuator 19 is connected to the conductive path 1
For example, when a signal is sent from the sensor 16 via the control circuit 18, a part of the air in the conduction path 15 is leaked by periodically opening and closing the valve 19a. At this time, the pressure within the pressure chamber 14 of the relief valve 12 provided in the bypass passage 10 is reduced by a certain amount. In this way, when the alcohol concentration becomes higher than a predetermined value, exhaust gas bypass is prevented until the pressure in the intake passage 2 becomes higher by a certain amount than when the alcohol concentration is low. ing.

The operation and function of the supercharged engine configured as described above will be explained next. When the engine is driven, the exhaust gas flowing down the turbine 5 of the supercharger 4 causes the turbine 5 to rotate, and the rotation of the blower 6 in conjunction with this causes air to flow toward the engine body 1 for supercharging. This increases the output of the engine. and,
As the amount of exhaust gas flowing down the turbine 5 increases, the supercharging effect increases and the pressure in the intake passage 2 increases. If this pressure exceeds the set value, the supercharging pressure control device 11 stops working. As a result, part of the exhaust gas flows into the bypass passage 10, and the amount of exhaust gas flowing down the turbine 5 is limited. This limits the rotational speed of the turbine 5, that is, the amount of intake air supercharging, and suppresses a rise in pressure within the intake passage 2. In this case, the set supercharging pressure of the supercharging pressure control device 11 without being subjected to the correction action by the correction device 17 is set in advance to the same level as, for example, in the case of a conventional gasoline engine with this type of supercharger. By setting this, when mixed fuel with a low alcohol concentration or gasoline-only fuel is used, the maximum boost pressure is limited so as to be suitable for these fuels under the above setting conditions.

On the other hand, when the alcohol concentration in the mixed fuel of alcohol and gasoline exceeds a predetermined value, such as when the fuel to be refueled is changed, the alcohol concentration sensor 16 and the correction device 17 operate, and the basic settings The supercharging pressure control device 11 is automatically corrected so as to prevent exhaust gas bypass and increase the set supercharging pressure until the pressure in the intake passage 2 becomes a certain amount higher than under certain conditions. This increases the maximum supercharging capacity of the supercharger 4, increases the supercharging pressure in the intake passage 2, and compensates for the decrease in output due to the increase in alcohol concentration.

In other words, alcohol has a lower calorific value than gasoline, so when using a mixed fuel of alcohol and gasoline, the higher the alcohol concentration, the lower the output tends to be. By increasing supply pressure, it is possible to compensate for the decrease in output. In addition, alcohol has a higher latent heat of vaporization than gasoline and has the effect of lowering the combustion temperature depending on the alcohol concentration, so if you use only gasoline or the alcohol concentration is very low, there is a restriction that knocking will occur and the boost pressure will be reduced. However, it is possible to solve this problem at the same time and compensate for the decrease in output when the alcohol concentration is high by increasing the maximum boost pressure.

As mentioned above, in an engine equipped with a supercharger, the maximum boost pressure is controlled by the boost pressure control device, and the alcohol concentration in the mixed gas of alcohol and gasoline is controlled by the alcohol concentration sensor and correction device. When the amount of alcohol exceeds a predetermined value, the set boost pressure of the boost pressure control device is increased, so even when the alcohol concentration in the mixed fuel is low, the boost pressure increases more than necessary and the engine As the alcohol concentration increases, the supercharging capacity of the supercharger is automatically increased to prevent a drop in engine output, while preventing a situation where the durability of the engine is impaired. Therefore, it can be effectively applied to mixed fuels of alcohol and gasoline, allowing the use of fuels with different alcohol concentrations and regular gasoline as desired in such mixed fuels, and making it suitable for these arbitrary fuels. This allows the engine to work efficiently.

[Brief explanation of the drawing]

The figure is an explanatory view showing an embodiment of the supercharged engine of the present invention. 1...Engine body, 2...Intake passage, 3...
Exhaust passage, 4...turbocharger, 5...turbine, 6...blower, 8...carburizer (fuel supply device), 10...bypass passage, 11...supercharging pressure control device, 16...alcohol Concentration sensor, 17...
...correction device.

Claims (1)

[Claims] 1. A supercharger that supercharges intake air into the combustion chamber, and a supercharging pressure control device that suppresses an increase in supercharging pressure when the supercharging pressure of the intake air supercharged by this supercharger exceeds a set value. A supercharged engine comprising: a fuel supply device for supplying a mixed fuel made by mixing alcohol and gasoline; an alcohol concentration sensor for detecting alcohol concentration; A correction device for correcting the control characteristics of the pressure control device, and the boost pressure set in the boost pressure control device is increased when the alcohol concentration is above a predetermined value. Machine engine.